应用自动管电流调制技术不同探测器宽度对胸部CT图像质量及辐射剂量的影响

Effect of different width of detector with ATCM technique on CT image quality and radiation dose for chest

目的:探讨应用自动管电流调制(ATCM)技术行胸部CT扫描时,不同探测器宽度对CT图像质量及辐射剂量的影响。方法:应用GERevolutionCT机,采用ATCM技术对胸部仿真模体行CT扫描,扫描按照探测器宽度分为40 mm组和80 mm组,两组分别在10、15、20、25和30噪声指数(NI)级别下扫描。记录两组图像的容积CT剂量指数(CTDIvol)和剂量长度乘积(DLP)。测量并比较层厚为5 mm的轴位图像的标准差(SD)和信噪比(SNR)。采用双盲法对层厚为0.625 mm的轴位图像的磨玻璃密度结节(GGN)进行主观评分,应用Kappa检验评价两组间主观评分的一致性。结果:40 mm组在NI级别为10、15、20、25和30时的CTDIvol与80 mm组比较,分别降低了10.53%、9.69%、10.37%、9.64%和8.93%,DLP分别降低了21.57%、20.67%、22.57%、20.29%和19.36%,两组不同探测器宽度扫描对GGN主观评分无明显统计学差异,且两名观察者的一致性中等或良好。结论:宽度为40 mm的探测器扫描可在保证图像质量的情况下有效降低辐射剂量,而80 mm探测器扫描则可以显著缩短扫描时间,提高时间分辨率。

Objective:To explore the effect of different width of detector on CT image quality and radiation dose for chest when applied automatic tube current modulation(ATCM)to implement CT scan on chest.Methods:Applying GE Revolution CT machine and adopting ATCM technique to implement CT scan for simulate phantom of chest.The scans were divided into 40 mm group and 80 mm group as the width of detector,and the two groups underwent scan under different noise index(NI)(10,15,20,25),respectively.The CT dose index volume(CTDIvol)and dose length product(DLP)about images of two groups were recorded.And the standard deviation(SD)and signal noise ratio(SNR)of axial scan images when slice thickness was 5 mm were measured and compared.The double-blind method was adopted to implement subjective score for ground glass nodules(GGN)of axial scan images with 0.625 mm of slice width.And Kappa test was applied to evaluate the consistency of subjective scores between two groups.Results:Compared with that of 80 mm group,CTDIvol of 40 mm group was decreased by 10.53%,9.69%,10.37%,9.64%and 8.93%when NI was 10,15,20,25 and 30,respectively,and the DLPs of 40 mm group were decreased by 21.57%,20.67%,22.57%,20.29%and 19.36%,respectively.The difference of GGN subjective scores of the different widths of detector between two groups was no significant,and the consistency of two observers was medium or well.Conclusion:The detector with 40 mm width can effectively decrease radiation dose under ensuring the quality of image,while the detector with 80 mm width can significantly shorten the scan time and increasing time resolution.